Dye transfer process for forming motion picture sound track

ABSTRACT

A LIGHT-ABSORPTIVE IMAGE IS PLACED ON A RECORD SURFACE, SUCH AS A SOUND TRACK ON FILM, BY FORMING A HARDENED GELATIN OR SIMILAR ABSORPTIVE IMAGE, IMBIBING A DYE INTO THE IMAGE, TRANSFERRING THE DYE TO THE RECORD SURFACE AND FIXING OR MORDANTING THE DYE THEREIN. THE DYE, NORMALLY HIGHLY UNSTABLE, IS UNEXPECTEDLY LIGHT STABLE IN ITS MORDANTED FORM, AND ABSORBS RADIATION IN THE RANGE FROM ABOUT 650 TO 1000MM. SUITABLE DYES ARE CERTAIN CYANINE DYES.

United States Patent 3,592,648 DYE TRANSFER PROCESS FOR FORMING MOTIONPICTURE SOUND TRACK Juergen H. H. Keller and Robert H. Sprague,Chelmsford, Mass., assignors to lltek Corporation, Lexington, Mass. NoDrawing. Filed Apr. 4, 1969, Ser. No. 813,759 Int. Cl. G03c 5/14 U.S.C]. 96-39 3 Claims ABSTRACT OF THE DISCLOSURE A light-absorptive imageis placed on a record surface, such as a sound track on film, by forminga hardened gelatin or similar absorptive image, imbibing a dye into theimage, transferring the dye to the record surface and fixing 0rmordanting the dye therein. The dye, normally highly unstable, isunexpectedly light stable in its mordanted form, and absorbs radiationin the range from about 650 to 1000 mm. Suitable dyes are certaincyanine dyes.

BACKGROUND OF THE INVENTION In a number of arts, and the formation ofsound strips is typical of one such art, it is desirable to form apredetermined pattern of light-absorptive material on a surface. Thispattern must be highly light absorptive at least in a certain spectrumof radiation, and in the sound strip art, this spectrum generally shouldbe from about 650 to about 1000 mm., usually with a maximum responsearound 840 mm. This is the normal peak output of projector lamps.

The conventional way at present of producing sound strips is to form asilver photographic image corresponding to the predetermined pattern tobe recorded. This requires, therefore, that the complete photographicprocess of development, fixing, etc., be carried out for each soundstrip that is produced. It is highly desirable, therefore, to develop asimpler way to produce sound strips in which a single physical imagebody can be produced, and the light absorptive pattern reproducedrepetitively from this image body.

In the past, it has been impossible to devise such a repetitive processfor sound strips and similar uses. Among other things, the dyes whichmight be useful in a dye-transfer process have been characterized byhaving the wrong spectral absorption or by being unstable. Therequirements of a dye for use in a transfer process include a number ofchemical and physical chemical properties such as solubility in water,and the ability to diffuse into a gelatin or similar layer, coupled withthe ability to be diffused out of the layer and fixed onto animage-receiving surface. These properties have been found in a number ofmaterials for conventional photographic purposes, and expertphotographers still believe that the best color photographs are made bya dye transfer process. Unhappily, similar dyes having absorptive peaksin the infra-red ranges are not readily available or are highlyunstable.

SUMMARY OF THE INVENTION We have now found that certain dyes arenormally highly unstable to the extent that in bulk or in solution theybleach out almost immediately in normal room light, but when employedaccording to our invention, do produce a sound strip having anunexpected degree of stability. This is all the more unexpected becausetheir normal use as sensitizing dyes depends on their being easily madecolorless or dissolved out of a photo- 3,592,648 Patented July 13, 1971graphic emulsion. A preferred species of dye, as described herein, hasbeen prepared.

According to the present invention, a dye of the desired class isdissolved in aqueous solution, is imbibed into a preformed image ofgelatin or similar material, corresponding to a record to be produced,is transferred from said image to the record surface, and is fixed ormordanted on the record surface to form a light stable record capable ofabsorbing radiation in the range from about 650 to about 1000millimicrons with a substantial or peak response in the range of about841 millimicrons. In a presently preferred form of the invention, therecord being produced is a sound track.

According to this invention, a color material is imbibed into a masterimage material and transferred to a recording surface wherein it isfixed. It is understood that the imbibed color material may be one oftwo reactive materials operable to form an insoluble, light stableradiation absorber, the other material being contained on or in therecording surface.

The type of dye material which has been found satisfactory is one whichis soluble in aqueous solution and capable of being diffused either intoa gelatin layer or into a similar layer such as an acrylic coating ormixed acrylic-gelatin coating or other layer conventionally used in thephotographic industry. It is capable of being fixed onto the recordsurface by means of a mordant or the like. Its spectral absorption isessentially in the 650 mm. to 1000 mm. range, and preferably peaks atabout 840 mm. In aqueous solution, it is highly unstable and issubstantially bleached out almost immediately in ordinary room light. Inmordanted form such as a salt of a heavy metal such as thorium or thelike or a polymeric salt-forming material, it is extremely light stableand is capable of being essentially permanently affixed to a surface, isessentially non-diffusing, and efiectively absorbs radiation from usualprojector lamps.

A suitable dye material has the general formula:

R and R are benzyl or lower alkyl;

Y=suitable cation, such as alkali or alkaline earth metal cation, e.g.,Na K and Li+.

X and X are the same or different elements necessary to complete athiazole or substituted thiazole ring or a benzoxazole or naphthoxazolering.

While X and X in the general formula may be the same or different, ithas generally been found that the specular absorption of the dyematerial is in the preferred specular region if X and X represent theole ments to complete a thiazole or substituted thiazole ring when nequals 3, and if X, and X represent the elements necessary to complete abenzoxazole or naphthoxazole ring when n equals 4.

DETAILED DESCRIPTION OF THE INVENTION A number of dye images have beenformed and transferred to a suitable record base such as a support basefor a sound track. For the purpose of comparative analysis, thefollowing examples will be presented employing the same dye material ineach example and employing reproducible procedures for the production ofimages on which measurements can conveniently be made. Thus, a steptablet was employed in these examples instead of a sound track as apreferred means of obtaining meaningful measurements.

EXAMPLE I A dye material was prepared as follows:

2-methylbenzothiazole 7.4 grams were combined with 6 grams of1,3-propane sulfone and heated for 2 /2 hours on an oil-bath at 145. Theresulting sticky mass was dissolved in methanol. Acetone was added andon standing crystals formed, which were filtered off, washed withacetone and dried. 3.8 grams of quaternary salt were obtained.

2.4 grams of the above material was combined with 2.2 grams ofglutaconaldehyde dianilide hydrochloride in 60 cc. absolute ethanol. 2grams of piperidine were added and the mixture was stirred for minutesat room temperature. A heavy precipitate formed during this time. Theprecipitate was filtered off and washed with methanol and acetone. Afterdrying a crude material was obtained, and dissolved in boiling methanol.The solution was filtered hot, concentrated to about /2 its volume andcooled. After filtration, washing and drying golden-green crystals wereobtained.

The dye, anhydro 3,3'-bis (3-sulfopropyl) thiatricarbocyanine hydroxide,piperidine salt, has the following structural formula:

A hardened gelatin matrix was made by normal photographic procedures(for example silver halide or photoconductor emulsion gelatin reliefimages, e.g., U.S. Ser. Nos. 712,931, 713,022, 713,212 all filed on Mar.14, 1968) from a sheet of commercially available matrix film. The filmwas exposed through a silver step tablet. After exposure and processingto form a hardened gelatin matrix, the matrix was dyed by immersing in a0.2% aqueous solution of dye brought to pH 3.6 by the addition of /2 byvolume of 10% acetic acid. After dyeing, the matrix was twice rinsedwith 1% acetic acid to remove surface dye.

Commercial dye transfer paper was conditioned at 50 C. The dyed matrixwas also conditioned to 50 C. (without drying), and the dyed surface ofthe matrix was placed in contact with the active surface of the dyetransfer paper for two minutes at 50 C. The two layers were thenseparated, and the image of the dye material was found to be transferredto the dye transfer paper, and mordanted therein by the transfer papersmordant. D,,,,,,, of the transferred dye was 2.5, and D was 0.19.

The dye image on the transfer paper was then exposed to radiationincluding infra-red radiation by placing it in the film-mounting portionof a commercial 35 mm. photographic projector using a 300 wattprojection lamp. The projector was not blower cooled, and thetemperature inside the projector was not externally controlled. At theend of a 2 hour exposure in the projector, there was no visible decreasein color and the measured D,,,,,,, of the image remained at 2.5.

EXAMPLE II A hardened gelatin matrix was prepared and dyed according tothe procedure of Example I. It was then transferred to a film substratecoated with a gelatin layer containing poly-4-vinyl pyridinemetho-p-toluene sulfonate as a polymeric mordant. The resulting D was0.78, D 0.05. The transferred mordanted dye image was stable uponexposure to intense infrared light as in a photographic projector.

4- EXAMPLE in EXAMPLE IV The matrix employed in Example III was dyed andrinsed. It was thereafter transferred to the film employed in Example IIincluding as a polymeric mordant poly- 4-vinyl pyridine metho-p-toluenesulfonate. D of the transferred dye was 0.97, D was 0.03. Thetransferred mordanted dye image was light stable.

EXAMPLE V The mordanted gelatin layer of Example II was directly dyed byimmersion in a 0.2 solution of the dye at a pH of 3.6, and a temperatureof 50 C. for 3 minutes. After rinsing and drying, the film was uniformlydyed, and had a D of 1.5. The color and density of the layer was notvisibly changed on exposure of the layer in a projector such asdisclosed in Example I.

EXAMPLE VI The procedures of Examples I through V may be employed forthe formation of sound tracks conventionally used in moving picturefilm. The resulting sound tracks have a high absorption density,particularly in the range of about 650 to about 1000 mm., and morespecifically in the range of about 840 mm. which corresponds typicallyto approximately the maximum emission range of ordinary sound projectorlamps. The sound track is highly efiicient in the absorption of lightfrom such lamps, and is virtually completely stable for exposures tosuch radiation corresponding to the use of sound tracks for manyhundreds of performances.

In addition to the dye employed in Examples I through V, there may alsobe employed other members of the class corresponding to the generalformula:

In the formula, X and X 11, Y and R and R have the values hereinbeforedefined.

In addition to the dyes according to this formula, dyes where Xrepresents elements to complete a quinaldine ring appear suited to thisinvention. Specifically, the following two dyes are noted:

l czrnsoi- N CgHiS O i-Na In general, it has been found that the lightabsorption characteristics of the dyes are closely in line with themaximum emission of projector lamps particularly where there is theproper interrelationship between the chain length designated by n, andthe ring structure as designated by X and X For example, where n is 3,it is preferred to use a thiazole or a substituted thiazole ringcompound to produce the spectral range most suited to sound strips. Whenn is 4 it is preferred to use ring elements corresponding to abenzoxazole or naphthoxazole ring. It has also been found that employingbenzyl or lower alkyl radicals has only a very slight elfect on thespectral absorption range.

It has previously been known that dye materials of this general formulacan be prepared, and such dye materials are generally characterized bybeing highly absorptive of radiation in specific spectral ranges, ofbeing rapidly decomposed by such radiation, and by being capable oftransferring the energy absorbed from such radiation within aphotographic film structure, to a silver halide complex in such mannerthat these materials are satisfactory photosensitizing dyes. It has nowbeen demonstrated that the materials according to the present inventioncan be fixed in an insoluble form such as for example by mordanting andwhen so made insoluble, are light stable and are particularly wellsuited for the producton of sound tracks and for other uses Where thedye must be stable to the absorbed light.

The mordant according to this invention is a heavy metal, polymeric, orother salt-forming material incorporated in the record member andcapable of forming an insoluble, essentially non-difiusing salt of thedye. A wide variety of mordants are known to be useful mordants inphotographic chemistry, and one skilled in the art can select aconvenient mordant for use in this invention. Suitable mordants aredisclosed, for example, in Belgian Pat. No. 657,788, issued Apr. 30,1965, in U.S. Pat. No. 2,839,401, in U.S. Pat. No. 2,945,006, in U.S.Pat. No. 2,768,078 and in numerous other patents.

What is claimed is:

1. A method of producing light-stable dye images from a repetitivelyuseful master comprising forming a hardened gelatin master patterncorresponding to an image to be formed, imbibing into the hardenedgelatin a dye having the formula:

wherein:

n is 3 or 4;

R and R are benzyl or lower alkyl;

Y=suitable cation;

X and X are the same or different elements necessary to complete athiazole or substituted thiazole ring or a benzoxazole or naphthoxazolering, and transferring the imbibed dye to a mordant-containing surface.

2. The process of claim 1 wherein the dye is anhydro- 3,3 bis(3sulfopropyl)thiatricarbocyanine hydroxide, ipiperidinesalt.

3. A method of forming sound tracks from a dye having the formula:

s s Xl C=oH-(o11=oH),.-o X, N IIMSOFY+ {12S 03' wherein:

n is 3 or 4; R and R are benzyl or lower alkyl;

References Cited UNITED STATES PATENTS 2,382,670 8/1945 Seymour et al101-464 2,675,316 4/1954 Carroll et a1. 101-464 2,882,156 4/1959 Minsk101-464 NORMAN G. TORCHIN, Primary Examiner J. WINKELMAN, AssistantExaminer U.S. Cl. X.R. 101-464

